American Eel Dynamics (American Eel Dynamics (Anguilla Anguilla rostratarostrata) in Hudson River ) in Hudson River

Tributaries, New YorkTributaries, New York

Leonard S. Machut1, Karin E. Limburg1, and Robert E. Schmidt2

1 - SUNY College of Environmental Science & Forestry

2 – Simons Rock College

http://www.nanfa.org/akiweb/974.JPG

Goals/Research QuestionsGoals/Research Questions Extend results of previous studies intoExtend results of previous studies into

tributaries of the Hudson Rivertributaries of the Hudson River EelEel Population Population

Where are they?Where are they?

What are their condition?What are their condition?

Nematode infection Nematode infection Prevalence?Prevalence?

Intensity?Intensity?

Wynants Kill, 7 Barriers

Saw Kill,7 Barriers

Hannacroix Creek5 Barriers

Black Creek9 Barriers

Minisceongo Creek7 Barriers

Peekskill Hollow4 BarriersStratified random Stratified random

sampling for lab sampling for lab analysisanalysis

− 232 of 1938 232 of 1938 capturedcaptured

Table 1: Watershed Characteristics for Censused Hudson River Tributaries

Tributary Name

Watershed Stream Eel Number of Distance to % Artificial

Area (km2) Length (km) Penetration (km)a Barriers 1st Barrier (m) Barrier

Wynants Kill 85.47 25.95 5 7 20 43

Hannacroix Creek 166.24 37.81 31 4 1985 40

Saw Kill 66.29 22.62 11 7 255 43

Black Creek 87.77 29.55 27.5 9 2620 22

Peekskill Hollow 135.51 28.11 23.5 4 3825 100

Minisceongo Creek 47.9 18.86 9 6 1900 100

a - Approximate distance upstream at which no eels were collected. We take this as an index of the degree to which eels penetrate and occupy a particular tributary.

Barriers: An Important RoleBarriers: An Important Role

0

3000

6000

9000

12000

15000

18000

0 5000 10000 15000 20000 25000 30000

Distance Upstream (m)

Ee

l De

ns

ity

Saw Kill

Hannacroix Creek

Black Creek

Multiple Barriers

Single Barrier

0

2000

4000

6000

8000

10000

12000

14000

0 5000 10000 15000 20000 25000

Distance Upstream (m)

Ee

l De

ns

ity

Minisceongo Creek

Peekskill Hollow

Wynants Kill

Multiple Barriers

Single Barrier

Barriers: An Important RoleBarriers: An Important Role(cont’d.)(cont’d.)

Tributary PopulationsTributary Populations

Multiple Regression

Ln(P) = 26.166 – 2.730*Ln(B) – 0.165*D + 1.359*U

where: P = Population

B = Number of Barriers

D = Distance Group

U = Subcatchment Urbanization

– r2 = 0.65, p < 0.001

Size DistributionSize Distribution

0

20

40

60

80

100

120

140

50

100

150

200

250

300

350

400

450

500

550

600

650

700

Eel Total Length (mm)

Fre

qu

en

cy

Length of Hudson River mainstem eelsLength of Hudson River mainstem eels

0%

20%

40%

60%

80%

100%50

100

150

200

250

300

350

400

450

500

550

600

650

700

850

Eel Total Length (mm)

Pro

po

rtio

n o

f T

ota

l .

Below 2nd Barrier Above 2nd Barrier

Size matters!Size matters!

355 594 317 215 202 35 22355 594 317 215 202 35 22 8 4 2 18 4 2 1131

22 12 15

Standardized residuals of eel wet weight

regressed against total length

Ex.) An eel of -1 is 1 S. D. lighter than average

Eel ConditionEel Condition

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

0-10% 10-20% 20-30% 40+%

Riparian Urbanization

Ee

l C

on

dit

ion

-1.2

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0 0-100 100-500 500-1000

BII Class

Eel

Co

nd

itio

n

Percent Riparian Urbanization Determined by Gap Analysis

BII = Barrier Intensity Index

2HeightBarrierCumulativekmBarriersBII */

Impacts of Barrier Intensity

BII0: Ln(TL) = 0.5667(Ln Age) + 4.3435; R2 = 0.90

BII0.1-100: Ln(TL) = 0.6128(Ln Age) + 4.4842; R2 = 0.85

BII>100: Ln(TL) = 0.8156(Ln Age) + 4.1468; R2 = 0.76

4

4.5

5

5.5

6

6.5

7

0 0.5 1 1.5 2 2.5 3 3.5

LN Age (yrs.)

LN

To

tal L

eng

th (

mm

)

BII = 0

BII = 0.1-100

BII = 100+

As barrier intensity increases, eels able to reach these habitats grow faster

Nematode Infection

Anguillicola Crassus - swimbladder parasite

Morrison & Secor, 2003 – Hudson River

1997 – prevalence less than 20%

2000 – prevalence over 60%

Intensity rose from <4 to 3.2 - 23.7

nematodes/eel

Tributary Invasion

2003 & 04 Sampling

Range = 0-20 nematodes/eel

Prevalence (P) = 39.2%

Intensity (I) = 2.44 nematodes/infected eel

Wynants KillWynants Kill

P = 51.9%P = 51.9%

I = 2.36I = 2.36

- http://www.dnr.cornell.edu/hydro2/hmap.gif

HannacroixHannacroix

P = 35.7%P = 35.7%

I = 2.60I = 2.60

Saw KillSaw Kill

P = 34.5%P = 34.5%

I = 1.70I = 1.70

Black CreekBlack Creek

P = 31.6%P = 31.6%

I = 2.25I = 2.25

MinisceongaMinisceonga

P = 40.4%P = 40.4%

I = 2.57I = 2.57

PeekskillPeekskill

P = 43.6%P = 43.6%

I = 2.77I = 2.77

Morrison and Secor, Morrison and Secor, 20032003

Prevalence = 60% Prevalence = 60%

Intensity = 3.2-23.7Intensity = 3.2-23.7

Country Eels?

Not significant (p = 0.14) but an upward trend as urbanization increases

0%5%

10%15%20%25%30%35%40%45%

Wat

ersh

ed U

rban

izat

ion

0.0

0.5

1.0

1.5

2.0

2.5

Mea

n A

bu

nd

ance

Watershed Urbanization

Abundance

What does this mean?

The Silver Lining…

Barriers are slowing nematode Barriers are slowing nematode invasioninvasion

05

101520253035404550

0 1 2 3 4 5 6 7 8 9

Barriers Crossed

Pre

vale

nce

(%

) .

0.0

1.0

2.0

3.0

4.0

5.0

6.0

Mea

n I

nte

nsi

ty

.

Prevalence

Intensity

Eel Condition

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

0 200 400 600 800

Total Length

Ee

l Co

nd

itio

n

Healthy

Infected

No significant difference

In Summary

The first barrier appears to reduce eel

densities by at least a factor of 10

Increased urbanization negatively affects

eel health

Infection with Anguillicola crassus is lower

in tributaries than the Hudson mainstem

A. crassus invasion is ongoing – dams may

slow infection rates in tributaries

A special thanks to:

Evan Leibu, Adlai Lang, Nsekan Smith,

Jackie Andersen, Emilio Menvielle, Omar Gordon,

Paul Simonin, Bob Daniels,

and the Hudson River Foundation

References available upon request @ lsmachut@syr.edu

Questions?

http://www.nanfa.org/akiweb/974.JPG